ISSN:0002-9505    

DOI:10.1119/1.16534

出版商:American Association of Physics Teachers    

年代:1991

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.16536

出版商:American Association of Physics Teachers    

年代:1991

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.16537

出版商:American Association of Physics Teachers    

年代:1991

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.16539

出版商:American Association of Physics Teachers    

年代:1991

数据来源: AIP

摘要:

A series of experiments is reviewed on precision measurements of the diffraction of slow neutrons paralleling those with light: diffraction at an absorbing edge, at an absorbing wire, and at single‐ and double‐slit assemblies. Besides their educational value, the experimental results also provide precise confirmations of the theoretical predictions as calculated via a Fresnel–Kirchhoff approach. The intensity in all these experiments was so low that the formation of the interference patterns individual neutron by individual neutron could easily be observed. The experiments are presented and analyzed in a way suitable for undergraduate teaching.

ISSN:0002-9505    

DOI:10.1119/1.16540

出版商:American Association of Physics Teachers    

年代:1991

数据来源: AIP

摘要:

Newton asserted without proof that a zero‐order rainbow exists, one associated with two refractions and no reflection. Subsequent authors also postulated such a rainbow but argued that it is not seen because its angular position (26 deg) is too close to the Sun. But it is not seen because it does not exist. Newton’s erroneous 26‐deg rainbow appears to have resulted from his failure to account for the dependence on angle of incidence of the solid angle of twice‐refracted rays corresponding to a given bundle of incident rays.

ISSN:0002-9505    

DOI:10.1119/1.16541

出版商:American Association of Physics Teachers    

年代:1991

数据来源: AIP

摘要:

The output power characteristics of a He–Ne laser are studied as an illustration of a four‐level gas laser excitation scheme. A linear dependence of the output power on the pumping rate is deduced from measurements of the output power as a function of the excitation current for various cavity lifetimes. These investigations are suitable for a laboratory course for advanced physics students.

ISSN:0002-9505    

DOI:10.1119/1.16542

出版商:American Association of Physics Teachers    

年代:1991

数据来源: AIP

摘要:

The invention of the ‘‘Y‐suspended’’ pendulum in 1815 by James Dean and analyzed in the same year by Nathaniel Bowditch has been discussed by Crowell [Am. J. Phys.49, 452–454 (1981)]. It was reinvented by Hugh Blackburn in approximately 1844 while he was a student at Cambridge and is frequently referred to as the ‘‘Blackburn pendulum’’ in the literature. The history of this device for demonstrating harmonic motion is traced. Blackburn was professor of mathematics at the University of Glasgow for 30 years, and a biographical sketch of him is included.

ISSN:0002-9505    

DOI:10.1119/1.16543

出版商:American Association of Physics Teachers    

年代:1991

数据来源: AIP

摘要:

The Schrödinger equation for two (or more) particles can sometimes be separated into two (or more) one‐particle equations. However, the boundary conditions can recouple the variables even though the Schrödinger equation itself is separable.

ISSN:0002-9505    

DOI:10.1119/1.16544

出版商:American Association of Physics Teachers    

年代:1991

数据来源: AIP

摘要:

The equilibrium probability distribution of a lattice gas with short‐range binary interaction is obtained. Numerical analysis shows the appearance of two peaks of such distribution for sufficiently low temperatures. This implies the onset of a first‐order phase transition. From the possible behaviors of the distribution (one peak, two peaks, or a ‘‘plateau’’), a splitting of the thermodynamic space of the system is reported. This splitting is macroscopically (thermodynamically) interpreted in the light of the behavior of the isotherms obtained from the thermal equation of state.

ISSN:0002-9505    

DOI:10.1119/1.16545

出版商:American Association of Physics Teachers    

年代:1991

数据来源: AIP